Performance of Floating Biofiltration in Methane Oxidation

Waste lagoons in the livestock industry are significant sources of methane (CH₄), a potent greenhouse gas that contributes substantially to climate change. Biofiltration, which relies on microbial oxidation, has emerged as a sustainable and effective method for mitigating methane emissions. This study introduces a novel floating biofiltration system designed to enhance methane removal directly from the surface of waste lagoons using integrated compost- and plant-based floating biofilters. Four biofilter configurations were evaluated over a four-month period: compost-only, plant-only (using cattail Typha spp.), and two mixed compost–plant systems. The performance of these setups was assessed by monitoring oxidation efficiency, microbial population dynamics, nutrient availability, moisture content, and the maximum methane oxidation rate (Vₘₐₓ). The mixed compost–plant configurations achieved the highest methane removal efficiency, reaching up to around 70% and the highest Vₘₐₓ of 3.1–3.9 μmol CH₄ g⁻¹ h⁻¹ under the middle condition. These setups also showed a notable increase in methanotroph populations, with Type I in compost reaching 32.8% after four months and Type II near roots peaking at 19.4% after two months. In comparison, the compost-only system reached a removal efficiency of around 60% with a Vₘₐₓ of 2.3 μmol CH₄ g⁻¹ h⁻¹ and Type I abundance increasing steadily from 3.5% to 32.8%, while the plant-only setup achieved a removal efficiency of around 50% and a Vₘₐₓ of 1.9 μmol CH₄ g⁻¹ h⁻¹, with Type II abundance declining from 19.4% at two months to 8–11% during dormancy. The vegetation helped maintain favorable moisture conditions and released root exudates that stimulated microbial activity. However, this beneficial effect declined during plant dormancy, highlighting a key limitation for year-round applications. Moreover, the linear relationship between surface methane concentration and methane flux in these systems was confirmed, consistent with previous studies conducted in other methane-oxidizing systems. These findings demonstrate that incorporating cattail into floating biofilters can significantly improve methane mitigation from waste lagoons. While the mixed biofilter design shows strong potential for scalable, nature-based methane reduction strategies, its seasonal variability warrants further optimization for consistent year-round performance in livestock waste management systems.